The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

"Once again lawyers are running the government's policy, not the government when it comes to asylum seekers," he told ABC radio.

Australian Greens senator Sarah Hanson-Young says the interview process must be set out in law.

"I've been very concerned that this process is so informal, that there's no proper legal representation in these interviews," she told ABC radio.

Rather than assessing the claims to determine whether people were entitled to protection, the government had been more concerned with "the grubby, dirty politics in a competition with (Opposition Leader) Tony Abbott", she said.

Labor also was intent on giving the impression "hordes" of people were being returned to Sri Lanka, Senator Hanson-Young said.

She wants federal legislation to be changed to stop would-be refugees being returned to dangerous situations in their home countries.

Senator Hanson-Young noted about 600 Sri Lankan asylum seekers had already been returned by the government.

"We need to change the way these processes are being done so that people are not deported back to danger and so that we know we're not breaching our obligations to very genuine refugees," she told reporters in Canberra.

Senator Hanson-Young urged the government to properly assess asylum seekers before deciding to deport them.

"Everybody has the right, if you arrive in Australia, to seek asylum," she said.